By way of background, the application of electrical current to the heart through electrodes either applied directly to the chest or through an implanted device is well known in the art. Typical implanted devices include defibrillators and/or pacemakers. These types of devices are usually surgically implanted into a subject and an intracavitary electrode is placed within or adjacent to the heart, typically transvenously.
While these implanted stimulating devices competently carry out their design task, there are many instances in which it would be desirable to electrically stimulate a portion of the heart that is either difficult to reach with a transvenously disposed electrode or which has been previously connected to an implanted electrode. For example, locations such as, but not limited to, the left ventricular apex, the anterior-basal left ventricular free wall, and the left atrium near the pulmonary veins. It may be necessary and advantageous to electrically stimulate the heart from these regions for reasons including multi-site pacing for congestive heart failure, single or multi-site pacing to prevent a ventricular or atrial tachyrhythmia, single or multi-site pacing very soon after the onset of an arrhythmia to halt the arrhythmia before it degenerates into ventricular or atrial fibrillation requiring a defibrillation shock, and multi-site electrodes for delivery of shocks with a lower defibrillation threshold than shocks delivered only through transvenous electrodes.
While electrodes on catheters inserted into veins of the heart by way of the coronary sinus can be placed in many cardiac locations, there are a number of spots or locations to which they cannot reach or be placed. Electrodes can be placed in almost any desired epicardial location during open-heart surgery. However, such surgery is expensive and is associated with both mortality and morbidity of the subject. With the advent of thoracoscopic surgery, it is now possible to implant such electrodes in the pericardial space by a much more minor procedure that requires only one or two small incisions for the insertion of a thoracoscopic device. However, this type of procedure is still complicated by the fact that the electrodes still must be connected to wires that are tunneled through the body to the pacemaker or defibrillator.
It has been recognized that the heart is under profound control of the autonomic nervous system. There are many instances when electrical stimulation of the neural input to the heart could be beneficial for the alteration of cardiac electrophysiologic status. The difficulty in implementing neural stimulation of the heart has been in the development of an apparatus for the direct stimulation or inhibition of cardiac sympathetic and parasympathetic nerves.
Accordingly, it would be advantageous and desirable to have an apparatus and method for stimulating portions of the heart which are difficult or impossible to reach or stimulate with a transvenous electrode but which are accessible utilizing the less invasive thoracoscopic surgical technique and which is able to stimulate the remote regions of the heart without the necessity for tunneling wires through a body of the subject and connection to a pacemaker or defibrillator for a source of electrical stimuli.
Furthermore, it would also be advantageous and desirable to have a method and apparatus which allows for the selective stimulation of the heart.